1. Field of the Invention
Embodiments discussed herein are related to a method of manufacturing a semiconductor device.
2. Description of the Related Art
In a semiconductor device (semiconductor apparatus) that uses a silicon (Si) semiconductor, a silicon carbide (SiC) semiconductor, etc., an ohmic contact (electrical contact portion) of a semiconductor portion and a transition metal layer (electrode) is conventionally formed by heat treatment (annealing).
To form such an ohmic contact, a method has been proposed that includes a process of depositing a transition metal layer on a surface of a semiconductor substrate (hereinafter, silicon substrate) formed of a silicon semiconductor, and heat treating the transition metal layer, where the heat treatment is performed at a temperature of 400 degrees C. to 750 degrees C. for 30 seconds to 90 seconds to heat the entire silicon substrate (for example, refer to Japanese Laid-Open Patent Publication No. 2012-246216).
Another method has been proposed where a transition metal layer is vapor deposited at a contact on a silicon carbide substrate and subject to rapid heat treatment at a temperature of 1000 degrees C. for 2 minutes whereby the entire silicon carbide substrate is heated and a carbon-rich silicide electrode is formed (for example, refer to Japanese Laid-Open Patent Publication No. 2009-177102 (paragraph 0017)).
A further method has been proposed where a titanium (Ti) layer, an aluminum (Al) layer, and a silicon layer are sequentially formed on a silicon carbide substrate by sputtering to form a contact electrode, followed by annealing using laser light to form an alloy of the titanium, aluminum, and silicon included in the contact electrode and the silicon and the carbon included in the silicon carbide substrate (for example, refer to Japanese Laid-Open Patent Publication No. 2012-099599 (paragraphs 0042 to 0044)).
Yet another method has been proposed where ion injection is performed to form a source extension region and a drain extension region in a surface of a silicon semiconductor substrate, an absorber film is formed of a metal film and an insulting film that cover the entire source extension region and drain extension region including a gate electrode, and the source extension region and the drain extension region are subject to laser annealing by irradiating laser light on the absorber film (for example, refer to Japanese Laid-Open Patent Publication No. 2002-280548).
Still another method has been proposed that is characterized by including a process of using a gate electrode as a mask and implanting an impurity into a semiconductor layer; a process of forming an interlayer insulating film so as to cover a gate electrode; a process of forming on the interlayer insulating film, a light absorbing film from a metal having a higher melting point than the semiconductor layer; and a process of irradiating the light absorbing film with light and activating the impurity in the semiconductor layer by the heat generated from the light absorbing film absorbing the light (for example, refer to Japanese Laid-Open Patent Publication No. 2010-040545).
Another method has been proposed where an object to be subject to annealing and having an absorption layer formed on a silicon carbide layer and a silicon carbide layer is prepared; the absorption layer of the object is irradiated and caused to generate heat by the energy of the laser beam absorbed by the absorption layer; and the silicon carbide layer is heated by the heat generated by the absorption layer (for example, refer to Japanese Laid-Open Patent Publication No. 2012-069748).
Nonetheless, with Japanese Laid-Open Patent Publication Nos. 2012-246216 and 2009-177102, a portion forming the ohmic contact (i.e., the transition metal layer, an interface of the substrate and the transition metal layer) alone cannot be heated and the entire substrate (the entire device) is uniformly heated. For example, when an ohmic contact of the silicon carbide semiconductor portion and the transition metal layer is formed, as described above, heat treatment is performed at a high temperature of 1000 degrees C. or greater. Therefore, interface properties of the semiconductor portion and gate insulating film and/or the material configuring the device may degrade. In Japanese Laid-Open Patent Publication No. 2012-099599, since a predetermined area is selectively heated by irradiation via a laser for which the spot diameter has been reduced, the described problems occurring with respect to Japanese Laid-Open Patent Publication Nos. 2012-246216 and 2009-177102 can be resolved.
Nonetheless, in Japanese Laid-Open Patent Publication No. 2012-099599, the distance from a lens that converges the laser light, to the surface of the transition metal layer has to be equivalent over the entire surface of the transition metal layer. In other words, device structure has to be such that the device surface is flat without asperity. Therefore, when the distance from the lens that converges the laser light, to the surface of the transition metal layer is not constant such as with disposal of the transition metal layer in a trench side wall, chip side wall, etc., laser irradiation has to be performed according to conditions that correspond to such arrangement and therefore, not all of the transition metal layer can be simultaneously heated and throughput may decrease.
Further, with Japanese Laid-Open Patent Publication No. 2012-099599, since a predetermined region is selectively heated by laser irradiation, programming control of the irradiation locus and the irradiation position of the laser is complicated. Further, consequent to deviations in the position of laser irradiation, uneven irradiation may occur, contact resistivity may deviate, and constituent portions disposed around the transition metal layer (e.g., gate insulating film, etc.) other than the transition metal layer may be heated causing device properties to degrade. When the surface area of the transition metal layer is less than the area corresponding to the spot diameter of the laser, a problem arises in that the transition metal layer alone cannot be selectively heated.